Composite wooden board



June 16, 1953 F. FAHRNI COMPOSITE WOODEN BOARD Filed Jan. 31, 1950 Patented June 16, 1953 Fred Fahrni, Zurich, Switzerland Application January 31, 1950, Serial No. 141,409 In Germany April 25, 1942 22 Claims.

The object of the present invention is a process for the manufacturing of compound compressed plates made of layers of pieces of wood and, binding materials. V l

The products so far known of this type, made of Wood pieces and the likemixed with a binding substance, showed great disadvantages.

When the pieces of wood were of coarser splinter shaped material, the surface is too rough and unsuitable for many uses, as for instance for flooring, cabinet-makerswork and so on.

Where a finer material is used, which necessitated a larger amount of binding substances, such plates are too expensive, all the more when coarser pieces of wood are used and reduced to a finersmaterial, which necessitates a larger use of energy. e

In addition compressed masses out of fine material alone with water contents of 8% and over, when compressed hot, presented difiiculties, because the steam could not escape and steam bubbles spoiled the production.

vThis disadvantage can be obviated by placing a metal sieve or the like between the heated' press and the mass to be compressed, which however on the other hand makes it impossible to material, needin less binding substances." and finally a covering layer of fine, selected material the mass. so obtained being then compressed in one operation.

A major advantage of this process is that due to the presence of the said middle layer,

relatively coarse wood waste of any shape, colour and size without any great additional use of materials for binding may be used for making compound compressed well looking wood plates. The plate has, nevertheless, as a result of the special basic and covering layers, a perfectly fine and equal surface, so that its uses are almost endless.

The porous structure of the coarser inner layer serves simultaneously as a channel for steam so that on both sides smooth plates are obtained. s

More beautiful and smoother surfaces are obtained by keeping the outer layers damper than" the inner ones during the compression, so that the general development of steam is relatively slight. Thus warping of the plates will be avoided. I

relatively high tensile strength and It is further advantageous to add larger quantities of binding so as of substances ensuring a better appearance and resistance to outside influences to the pieces of wood destined to the outer layers than for the inner layer. Such sub-- stances consist for instance of waterproofing or additions in order to achieve a larger resistance to humidity, to harden the pieces of wood, colours of same, heightening of the powers of resistance against mildew and mold and so on. Thereby, in spite of a great reduction of production costs, the whole surface of the outer surface is particularly good and firm.

The present invention relates to wooden boards, and more particularly to composite wooden boards for building purposes, furniture and the like. V

This application isa continuation-in-part of my application Serial No. 630,619, filed November 24,- 1945, for A' Process for the Manufacturing of Compound Compressed Plates Made of Layers of Pieces of Wood and Binding Materials.

It is an object of the present invention to provide a wooden board consisting of an inner or core layer having good heat and sound insulat iIlg properties, and outer or texture layers having a relatively high mechanical strength.

It is another object of the present invention to provide a composite wooden board consisting of an inner or core layer having a relatively low density and outer-or texture layers having a being substantially impervious to water.

It is a further object of the present invention to provide a composite wooden board consisting of an inner or core layer having good heat and sound insulating properties and a relatively low density and outer or texture layers having a smooth outer surface and being substantially impervious to water.

According to this invention a wooden board comprises in combination, a thin layer of superposed unoriented fiat wood shavings arranged substantially parallel to the outer faces of the finished board, and an adhesive substance firmly connecting said fiat wood shavings directly to one another so that the fiat wood shavings firmly adhere directly to one ,another'and provide a wooden board substantially impervious to water and having a high tensile strength.

A composite wooden board according to the invention comprises in combination, a core layer of randomly arranged wood particles providing air spaces between themselves, a binder substance firmly connecting the randomly arranged wood shavings firmly adhere to one another and to the 1 porous core so as to provide on one side of. the

porous core a firmly adhering surfacelayer being substantially impervious to water andihayihg: a high tensile strength.

A preferred embodiment of the present invention comprises in combination a central layer of' randomly arranged wood particles providing air. spaces between themselves, a binder substance firmly connecting the randomly arranged wood particles so that the randomly arranged wood particles firmly adhere to one another and proe vide aporous core having good heat insulating properties, two relatively thin outer layers. arranged on opposite facesiof the porous core, respectively, and consisting of superposed unoriented flat wood shavings arranged substantially parallel to the outer facesof the finished board, and an adhesive substance connecting the flat wood shavings in each of the outer layers to one another and to the porous core whereby the flat Wood shavings firmly adhere directly to one other and to the porousoore so as to provide on both sides of the'porou's core firmly adhering surface layers being substantially impervious to water and having a high tensile strength.

Preferably thecentral core layer consists of .randomly arrangedsplinter-shaped wood particles providing air spaces between themselves whereas the two outer layers are arranged on opposite faces of the central core layer, respece tively, and consist each of compressed superposed unoriented flat shaving-shaped-wood particles arranged substantially parallel to the faces of the central core layer; an adhesive substance penetrates all the wood particles and firmly connects them to one another so that the same firmly adhere to one another and provide a finished composite wooden boardfcomprising a highly heat and sound insulating central core and firmlyadhering substantially water-impervious outer layers having a high tensile strength.

In an embodiment of the present invention the splinters of whichthe core material'consistshave a length of about'5 to mm; a width of about 5 to 10 mm., and a thickness not exceeding several mm. preferably of about 1 to several mm.

In an embodiment of the present invention the binder substance in the core layer amounts to a very small percentage, e. g., to ab o ut 3.5 to 4% by weight of the weight of the splinters.

In an embodiment of the present invention the binder substance in the outer layers amounts to a small percentage, e. g., to about 10;to 14 by weight of the weight of the shavings.

It should be noted that preferablythe percentage of binder substance in the outer layers is substantially larger than the percentage of the binder substance in the core layer.

In an embodiment of the present invention the number of the super-imposedshavings is at any part of any of the outer layers at least 2 and not more than 5.

In an embodiment of the present invention the core layer is substantially thicker than any of 4 the outer layers, i. e., has a thickness equal to several times the thickness of each of the outer layers. Each of these outer layers is relatively thin and has, e. g., a thickness of about 2 mm.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific. embodiments when read in connection with the accompanying drawings, in which:

Fig.1 is a sectional view of a composite wooden board according to the present invention;

Fig. 2 is.a plan View of an outer layer of the boarclshown in Fig. 1;

Fig. 3 isan enlarged view of part of Fig. 1;

Fig. 4 shows some of the splinters used for the central or core material of the board shown in Fig. 1; and

Fig. 5 shows some of the shavings forming part of the outer layer of the board shown in Fig. 1.

Referring now to the drawings and first to Fig. 1, the two outer layers of finer material I and 2 with mirror-smooth upper surfaces 3 or 4 are immediately recognizable as also the middle layer 5 0f coarser material.

The outer layers I and 2 of the composite wooden board are relatively thin and consist of superposed-unoriented fiat wood shavings 6 (Figs. 2 and 5) arranged substantially parallel to the outer faces of the finished board. An adhesive substance firmly connects the flat wood shavings directly to one another so that the flat wood shavings firmly adhere directly to one another and provide a wooden board I or 2 which is substantially impervious to water and has ,a high bending strength. At any part of the outer layer I or 2, the number of the superposed shavings is at least equal to 2 and less than 5,. as will be clearly seen from Figs. 1 and 3. The adhesive renders the outer surface 3 and 4 of the outer layers very smooth and like a mirror. The adhesive amounts to about 10 to 14 by weight of the weight of the shavings.

The shavings are preferably shaped substantially as parallelograms having the shorter sides I thereof out along the fibers 8 of the wood as clearly seen in Fig. 5. The longer sides 8 of the shavings are indented and run at an angle to the shorter side of the parallelogram'which is appreciablydiiferent from for instance equal to 30 or 45. Fig. 2 shows the shavings B in a finished board where they partly overlap one another and are distributed at random with their flat sides parallel to the finished board, and to the core layer presently to be described.

The central or core layer 5 consists of randomly arranged wood particles IIHFigs. 1, 3 and 4) which are preferably splinter-shaped so as to provide air spaces II between them which impart to the core layer a relatively low density and highlyheat and sound insulating properties. The wood splinters II) are firmly connected to one another by a binder substance which amounts preferably to about 3.5 to 4% by weight of the splinters. The splinters II) have preferably a length of between 5 to 50 mm., a width of between 5 to 10 mm, and a thickness of one to several mm.

The central or core layer is porous throughout whereas the outer layers of shavings are non porous and substantially impervious to water. Preferably the central layer has at least a thickmum of covering 'inaterial. 3. Following are'some examples of firmly to each other owing to the binder and adhesive substance and provide a finished composite wooden board comprising a highly heat and sound insulating central core and firmlyadhering substantially water impervious outer layers l and 2 having a high tensile strength.

Aprocess for manufacturing compositewooden boards according to the present invention is disclosed in my co-pending application Serial No. 130,970, filed December 3, 1949. According tothis application a relatively thin first layer-ofshavings to which a latent adhesive 'substance'gis admixedis spread on a carrier sheet; a relatively thick layer of ground wood particles to'which a latent plastic binder is admixed is spread on the first layer of shavings and a second relatively thin layer of shavings is spread on th layer of the ground core material. The whole'issubiected to a' pre-p'ressing operation and'lfinally' pressed in ahot press whereby the layers formathe compositeboard.

It should now be added-that it isexpedient that, when the outer layers are of a markedly finer material than the inner, these-latter should be compressedbefore th -finer layers are filled. By the pre-compressingof the coarser inner layers the projection of parts into the outer surface will be avoided and further the space between the single coarser pieces willbereduced, so thatcomplete covering may-be carried out .witha..miniexecution of the process according to the presentinvention: wd rl 1 1 a a i Waste from veneering, ends, and'furniture factories are so worked in asplitting 'ma-chine that pieces result between 5 and 50 mm. long,

about 5 to mm. wide and from one to-Hseveral millimeters thick. Other shorte'rand thicker little pieces'occu'rring do notmatter." This ma}- "terial is, possibly previously waterproofed with 2.5% parafiine; dried to a humidity 'content'of 5% and with a 3.5% of a binding substance, for

I instance a condensate of ureaformaldehyde "ob tained in powder form according toan already known process with the suitable catalysis, which j rapidly dissolves the binding substance Vin-question in the h'eat and then mixed with water;

Forthe covering layers the material is dusti freej clean white soft wood, planing shavings or other thinand fiat kinds of shavings, which arie mixed with 14% of binding substances and finally kept to a'humidity conten'tsof 18% by sprinkling with water.

single layers of as much previously selected coarser material as to produce when compressed, a thickness of 21 mm. .13.. '-These-twolayers canin some gcases .be Lprecompressed' 'and thereover singlellay'ers of glued -fla't shavings of the :same' mixture w-illiz'beiifilled' in' order to produce the coyering in up to 2 layer. 1' l s The whole mixture will: now she rapidlyprecompressed so; that it. becomes sufiicientlyzcoherenti and: provided. with .a. i.covering ;ilsheeti of metal, be compressed without framefinuforsinfurniture or cabinet-making, for doors as for its stance, a press heated to C. with 10 kg. pres% sure per square cm. y

'Ihe'product'obtained is a beatutiful, firm and on both sides very smooth plate with a pale,

veneer-like'surface, which is very suitablefor walls and ceiling coverings. The covering layers may also be stained, and polished and thus substiuted for expensive veneering.

Example 2 Uneven'waste, such as sawmill waste, splinters trunk disks, etc., are broken into coarser, splinter shaped parts and dried to about 4%. 800 parts of weight of this material are mixed, according to the already known process, with 32 parts of .weight of a binding substance, fed uniformly into -a form as described under (1) and pre-comwell as 50 parts of weight finer hard Wood saw.

shavings are mixed with 20 parts of weight of a waterproof binding substance and20 parts of weight of water. 10 parts of weight of hard wax powder are then added. The. mass thus mixed is uniformly distributed over the above described pre-compressed coarse layer and also submitted to a pre-compression in the frame. The main-compression without frame follows in the press heatedabout C. at a pressure of 25 kgs. per square cm.

The result is a plate of a beautiful, smooth and hard surface layer, specially suitable for flooring. Toobviate the danger of slipping, quartz powder, plaster or the like, may be added to the covering mass before or during the mixing with the binding substance.

In all cases the compression amalgamates the layers of the sheet into one body. Y

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of wooden boards differing from the types described above.

While I have illustrated and described the invention as embodied in a composite wooden generic or specific aspects of this invention and, therefore, such adaptations should and are in- .tended to be comprehended within the meaning and range of equivalence of the following claims.

, .Letters Patent is;

-I claim as new and desire to secure by .1.-A composite wooden board comprising in comprising in combination a core layer of randomly arranged wood particles providingv air spaces between themselves; a' binder substance firmly connecting'said randomly arranged wood particles without filling said air spaces so that said randomly arranged wood particles firmly adhere toone another and provide a porous core having oodheat insulating properties; an outer gamma 7. layer arranged on one iaceof said porous ;core and having a thickness which:is small as compared to the thickness of said .core,sai'd outer layer consisting of superposed unoriented fiat wood shavings; and an adhesive substance connecting-said fiat wood shavings directly to one another and to said porous core whereby saidlfiat wood shavings firmly adhere to one another and to said porous core so as to provide on one side of said porous core a firmly adhering surface layer being substantially impervious to water and-having a high tensile strength.

2. A composite wooden board comprising win combination a central layer of randomly arranged wood particles providing air spaces be- I tween themselves; a binder substance firmly connecting saidrandomly arranged wood particles without filling said air'spaces so that said randomly arranged wood particles firmly adhere to one another and provide a'porous core having good heat insulating properties;- two outer layers arrangedon opposite faces of said porous core, respectively, and having thicknesses, respectively, which are small as compared to the thickness of said core, said outer layers each consisting of superposed unoriented fiat wood shavings arranged substantially parallel to' the outer faces of the finished board; and anadhesive substance connecting said fiat wood shavings in each of said outer layers directly to one another and to said porous core whereby said flat wood shavings firmly adhere directly to one another and to said porous core so as to provide on both sides of said porous core firmly adhering surface layers being substantially impervious to water and having a high tensile strength.

3. A composite wooden board comprising in combination a central core layer of randomly arranged splinter-shaped wood particles providing air spaces between themselves; two outer layers arranged on opposite faces of said central core layer, respectively, and consisting of compressed superposed unoriented fiat shavingshaped wood particles; and an adhesive substance firmly connecting said flat shaving-shaped wood particles of said outer layers directly to'one another and said splinter-shaped wood particles of said core layer to one another without filling said air spaces between the same so that the layers firmly adhere'to one another and provide a fin- 'ished composite wooden board comprising a highly heat and sound insulating central core and firmly adhering substantially water impervious outer layers having a high tensile strength.

4 A composite wooden board comprising in.

combination a central core layer of randomly arranged splinter-shaped wood particles providing air spaces between themselves; two outer-layers arranged on opposite faces of said centralcore layer, respectively, and consisting of compressed superposed unoriented fiat shaving-shaped wood particles arranged substantially parallel to the faces of said central core layeryand an adhesive substance penetrating said flat-shavingshaped wood particles of said outer layers directly to one another and firmly connecting said-splinter-shaped wood particles of said-core layer to I one another without filling said air ,spacesabetween the same so that the layersfirmly adhere "to one another and provide a finishedicomposite wooden board comprising a highlyheat and sound insulating central core andjfirmly. adhering substantially water impervious outerzlayershavinga high tensile strength. i Y

-5. A composite wooden board comprising: in

as .aparallelogram; and an adhesive substance connecting saidfiatwood shavings directly to one another and tosaid porous core wherebysaid fiatwood shavings firmly adhere: to one. another and to, said porous coreso as to provide on one side of said porous ;core a firmly adheringsurface layer ,-being:-substantially imperviousto water and having a high. tensile strength.

6. A composite -:wooden board comprising in combinati0n,,a;layer of randomly arranged .wood splinters providing, air spaces betweenthemselves, said splinters having a length of about 5 to 50 .mm,,and a thickness of between one and several mm.; a binder substance firmly connecting said .randomlyarranged-wood splinters without filling said air spacesso that :said randomly arranged wood splinters firmly adhere to one another and provide-a porous core having good heat insulatingzproperties anda low d ensity; .an outer layer arranged on one face of said porous core and having a thicknesswhich is small as compared to r the thickness of saidcore, said outerlayer consisting of superposed unoriented fiat wood shavings each beingshaped substantiallyas 4a parallelogram, said shavings being arranged substantially parallel to the outer faces of the finished board and partly overlapping one another; and an adhesive substance connecting said flat wood shavings directly to one another and to said porous core whereby said fiat wood shavings firmly -adhere to one another and to said porous core .so as to provide on. one sideof said porous core a firmlyadhering surface layer beingsubstantially impervious to water and having a high tensile strength.

'7. A'composite wooden board comprising in combination, a layer of randomly arranged wood properties and a low density; an outer layer arrangedon one faceof said porous core and having a thickness which is small as compared to the thickness of said core, said;outer layer consisting of superposed unoriented fiat wood shavingseach :beingshaped substantially as a parallelogram,

: saidshavings being arranged; substantially parallel to the, outer faces; of the finished-board and partly overlapping one; another, the number; of

said superposed shavingsiheing at any part of -said;outer layerat least 2-andnot more than 5; and an adhesive substanceconnectingsaid fiat wood shavings directly to one;another-and {to said porous core whereby :said-flatwood shavings firmly adhere to one another and to said porous core s'oas to provide on oneside of said-porous core, afirmly adhering surface layer.being;sub-

1 stantially, imperviousto water.and'havingahigh tensile strength.

splinters providing air spaces between themselves, said splinters having a length of about to 50 mm. and a thickness of between one and several mm.; a binder substance firmly connecting said randomly arranged wood splinters without filling said air spaces so that said randomly arranged wood splinters firmly adhere to one another and provide a porous core having good heat insulating properties and a low density; an

outer layer arranged on one face of saidporous core and having a thickness which is small as compared to the thickness of said core, said outer layer consisting of superposed unoriented flat wood shavings each being shaped substantially as a parallelogram, said shavings being arranged substantially parallel to the outer faces of the finished board and partly overlapping one another, the number of said superposed shavings being at any part of said outer layer at least 2 and not more than '5; and an adhesive substance connecting said fiat wood shavings directly to one another and to said porous core, said binder substance amounting to about 3.5 to 4% by weight of said splinters and said adhesive substance amounting to about to 14% by weight of said shavings, whereby said fiat wood shavings firmly adhere to one another and to said porous core so as to provide on one side of said porous core a firmly adhering surface layer being substantially impervious to water and having a high tensile strength.

9. A composite wooden board, comprising in A shavings each being a binder substance firmly connecting said randomly arranged splinter-shaped wood particles without filling said air spaces so that said randomly arranged splinter-shaped wood particles firmly adhere to one another and provide a porous core having good heat insulating properties and a low density; two outer layers arranged on opposite faces of said porous core, respectively; and

having thicknesses, respectively, which are small as compared to the'thickness of said core, said outer layers each consisting of superposed unoriented fiat wood shavings each being shaped substantially as a parallelogram; and an adhesive substance connecting said flat wood shavings in I each of said outer layers directly to one another and to said porous core whereby said fiat wood shavings firmly adhere directly to one another and to said porous core so as to provide on both sides of said porous core firmly adhering surface layers being substantially impervious to water and having a high tensile strength.

10. A composite wooden board, comprising in combination, a central layer of randomly arranged splinter-shaped wood particles having a length of about 5 to mm. and a thickness of between one and several mm. and providing air 'spaces between themselves; a binder substance firmly connecting said randomly arranged splinter-shaped wood particles without filling said air spaces so that said randomly arranged splintershaped wood particles firmly adhere to one another and provide a porous core having good heat 'insulating properties and a low density; two outer layers arranged on opposite faces of said a porous core, respectively, and having thicknesses, respectively, which are small as compared to the thickness of said core, said outer layers each consisting of superposed unoriented flat wood ly adhere directly to one another and to said porous core so as to provide on both sides of said porous core firmly adhering surface layers being substantially impervious to water and having a high tensile strength.

11. A composite wooden board, comprisingin combination, a central layer of randomly arranged splinter-shaped wood particles of random length providing air spaces between themselves; a binder substance firmly connecting said randomly arranged splinter-shaped wood particles without filling said air spaces so that said randomly arranged splinter-shaped wood particles firmly adhere to one another and provide a porous core having good heat insulating properties and a low density; two outer layers arranged on opposite faces of said porous core, respectively, and having thicknesses, respectively, which are small as compared to the thickness of said core, said'outer layers each consisting of superposed unoriented fiat wood'shavings each being shaped substantially as a'parallelogram, said shavings being arranged substantially parallel to the outer faces of the finished board and partly overlapping one another, the number of said superposed shavings being at any part of said outer layer at least 2 and notmore than 5; and an adhesive substance connecting said fiat wood shavings in each of said outer layers directly to one another and to said porous core whereby said fiat wood shavings firmly adhere directly to one another and to said porous core so as to provide on both sides of said porous core firmly adhering surface layers being substantially impervious to water and having a high tensile strength. 7

12. A composite wooden board, comprising in combination, a center layer of randomly arranged splinter-shaped wood particles of random length providing air spaces between themselves; a binder substance firmly connecting said randomly arranged splinter-shaped wood particles without filling said air spaces so that said randomly arranged splinter-shaped wood particles firmly adhere to one another and provide a porous core having good heat insulating properties and a low density; two outer layers arranged on opposite faces of said porous core, respectively, and having thicknesses, respectively, which are small as compared to the thickness of said core, said outer layers each consisting of superposed unoriented fiat wood shavings each being shaped substantially as a parallelogram; and an'adhesive substance connecting said fiat wood shavings in each of said outer layers directly to one another and to saidporous core,

said binder'substance amounting to between 3.5

and 4% by weight of said splinter-shaped wood particles and said adhesive substance amounting to between 10 and 14% by weight of said shavings, whereby said fiat wood shavings firmly adhere directly to one another and to said porous core so as to provide on' both sides of said porous core firmly adhering surface layers being substantially impervious to water and having a high tensile strength.

13. A composite wooden board, comprising in combination, a central layer of randomly arranged splinter-shaped wood particles of random length providing air spaces between themselves;

".a binder substance firmly connecting said l I randomly arranged splinter-shaped wood particles without filling said air spaces so that said randomly arranged splinter-shaped wood particles firmly adhere to one, another and provide a porous core havinggood heat insulating prop-.

erties and a low'density; two outer layers arranged on opposite faces of said porous core, respectively, and having thicknesses, respectively, which are small as compared to the thickness of said core, said outer layers each consisting of superposed unoriented fiat wood shavings each being shaped substantially as a parallelogram having the shorter sidesthereof out along the fibre of the wood; and an adhesive substance connecting said fiat'wood shavings in each oi said outer layers directly-to. one anotherand to said porous core whereby saidflat wood shavings firmly adhere directly to one another and to said porous core so as to provide on both sides of said porous core firmly adhering surface layers being substantially impervious to water and having a high tensile strength.

14. A composite woodenboard,comprising in combination, a central .layer of randomly arranged splinter-shapedwood particles of random length providing air spaces between themselves; a binder substance firmly connecting said randomly arranged splinter-shaped wood particles without filling said air spaces so that said randomly arranged splinter-shaped wood particles firmly adhere to one another and provide a porous core having good heat insulating properties and a lowdensity; two outer'layers arranged on opposite faces of said porouscore, respectively, and having thicknesses, respectively, which are small as compared to the thickness of said core, said outer layers each consisting of superposed unoriented flat wood shavings each being shaped substantially as a parallelogram having the shorter sides thereof out along the. fibre of the Wood, the longer sides thereof being indented and running at an acute angle to said shorter sides, said shavings being-arranged substantially parallel to the outer faces of the finished board and partly overlapping one another; and an adhesive substance connecting said flat wood shavings in each of said outer layers directly to one another and to said porous core whereby said flat wood shavings firmlyadhere directly to one another and to said porous core soas to provide on both sides of said porous core :firmlyladhering surface layers being substantially impervious to water and having a high tensile strength.

15. A composite wooden board, comprising in combination a central layer of randomly arranged splinter-shaped wood particles having a length of about to 50 mm. and a thickness of between one and several mm., and providing air spaces between themselves; a binder substance firmly connecting said randomly arranged splinter-shaped wood particles without filling said air spaces so that said randomly arranged splinter-shaped wood particles firmly adhere to one another and provide a porous core having good heat insulating properties anda low density; two outer layers arranged on opposite faces of said porous core, respectively, and having thicknesses, respectively, which are small as compared to the thickness of said core, said outer layers each consisting of superposed unoriented fiat wood shavings each being shaped substantially as a parallelogram, said shavings being arranged substantially parallel to the outer faces of the finished board and partly overlapping one another, the number of :said superposed shavings being at any part. of saidouterilayenat least two and not morethan five; and; an adhesive subistance. connecting .said :fiat wood shavings. .in

shavings, whereby said fiat wood shavings-firmly radhereidirectly to one, another and to said-porous core so; as toprovide on both sides of1saidiporous core firmly; adhering; surface layers being :sub- :stantially imperviouszto' water andihaving arhigh tensile strength.

, 16. Aicomposite wooden board,;comprising:in

, combination a central, :layer of randomly .1 arranged splintereshaped woodparticles "having a length oi;abouta5 to;50;mm.;and a thickness of between one and .severalmm,,:.and providing *air spaces between themselves; a bindersubstance .firmly connecting said :randomly arranged splinterr-shaped :wood :particles without pfilling said air.;spaces so thatisaid randomly arranged wsplintereshaped wood particles firmly adhere to one another and provide a; porous core-having .good heat insulatingproperties anda low density; two outer layers each relatively thinner than said porous core. arranged on opposite faces thereof, respectively, and having thicknesses, respectively, whichiare smallas compared to the thickness of said core, said outer layers each consisting of superposed unoriented fiat wood shavings each being shaped substantially as a parallelogram having the shorter sides thereof cut along'the fibre of the wood, said vshaving-being-arranged substantially parallel "to the outer faces of the finished gboardrand :partly '.overlapping one another, the;.number"of said superposed shavings :being atanypart of saidouter layer atleast-two oandlnot more'thanrfive; and anradhesive sub- :stanceconnecting said=fiatwoodshavings in each of;said outerlayers directlyto one another and to :said =;poro,us core, said binder substance amounting to, approximately 13.5 to, !i% by weight [of said splintereshaped wood particles and said adhesivesubstance I amounting to approximately 10 to 14% by weight of said shavings, whereby said flat-Wood shavings firmly adhere directly to one another and tosaid porous-core so as to provide on ,bothsides'of .saidporous core firmly ad- .hering surface, layers being substantially impervious to water and having a high tensile strength.

1'7. A composite-,woodenboard, comprising in combination .a central layer of randomly arranged splinter-shaped wood particles having a length of about -5 to 50 mm. and a thickness of between oneandseveralmm, and providingair spaces between themselves; a binder substance firmly connecting said randomly arranged splinter-shaped wood particles without filling said air spaces so that said randomly arranged splinter-shaped wood particles firmly adhere 'to one another and'provide a porous core having good heat insulating properties and a low density; two outer layers arranged on opposite faces of said porous core, respectively, and having thicknesses, respectively, which are small as compared to the thickness of said core, said outer layers each consisting of superposed unoriented fiat wood shavings each being shaped substantially as a parallelogram having the shorter sides thereof out along the fibre of the Wood, the longer sides thereof being indented and running at ,an acute angle to said shorter sides, said shavings being arranged substantially parallel 13 V to the outer faces of the finished board and partly overlapping one another, the number of said superposed shavings being at any part of said outer layer'at least two and not more than five; and an adhesive substance connecting said fiat wood shavings in each of said outer layers directly to one another and to said porous core, said binder substance amounting to 3.5 to 4% by weight of said splinter-shaped Wood particles and said adhesive substance amounting to 10 to 14% by weight of said shavings, whereby said fiat wood shavings firmly adhere directly to one another and to said porous core so as to provide on both sides of said porous core firmly adhering surface layers being substantially impervious to water and having a high tensile strength.

18. A composite wooden board comprising in combination a central core layer of randomly arranged splinter-shaped wood particles pro-,-

viding air spaces between themselves; two'outer layers arranged on opposite faces of said central core layer, respectively, and consisting of compressed superposed fiat unoriented wood shavings; and an adhesive substance penetrating said wood shavings of said outer layers directly to one another and firmly connecting said splinter-shaped wood particles of said core layer to oneanother without filling said air spaces between the same so that the layers firmly adhere to one another and provide a finished composite wooden board comprising a highly heat and sound insulating central core and firmly adhering substantially water impervious outer layers having a high tensile strength, said outer layers of shavings having each a thickness of about 2 mm. and said central core layer having a thickness equal to several times the thickness of each core layer. v

19. A composite woodenboard comprising in combination a central core layer of randomly arranged splinter-shaped wood particles providing air spaces between themselves; two outer layers arranged on opposite faces of said central core layer, respectively, and consisting of compressed superposed unoriented fiat wood 1 shavings each being shaped substantially as a parallelogram having the shorter sides there- 'of out along the fibre of the wood, the longer sides thereof being indented, said shavings being arranged substantially parallel to the faces 0 of said central core layer; and an adhesive substance penetrating said fiat wood shavings of said outer layers directly to one another and firmly connecting said splinter-shaped woodparticles of said core layer to one another without filling said air spaces between the same so that the layers firmly adhere to one another and provide 'a finished composite wooden board comprising a highly heat and sound insulating central core and firmly adhering substantially water impervious outer layers having a high tensile strength.

20. A composite Wooden board comprising in combination a centralcore layer of randomly arranged splinter-shaped wood particles'providing air spaces between themselves; two outer layers arranged on opposite faces of said central core layer, respectively, and consisting of compressed superposed unoriented flat Wood shavings each being shaped substantially as a parallelogram having the shorter sides thereof out along the fibre of the wood, the longer sides thereof being indented, said shavings being arranged substantially parallel to the faces of said central core layer; and an adhesive substance penetrating said fiat wood shavings of said outer layers directly to one another and firmly connecting said splinter shaped wood particles of said core layer to one another without filling said air spaces between the same so that the layers firmly adhere to one another and provide a finished composite wooden board comprising a high- 1y heat and sound insulating central core and firmly adhering substantially water impervious outer layers having a high tensile strength, said central core layer having a thickness which is several times the thickness of each said outer layer.

21. A composite wooden board com-prising in combination-a core layer of randomly arranged wood particles; a binder substance firmly connecting said randomly arranged wood particles so. that said wood particles firmly adhere to one another and provide a porous core having good heat insulating properties; an outer layer arranged on one face of said core and having a pervious to water.

thickness which is small as compared to the thickness of said heat-insulating porous core,

said outer layer consisting of superposed unoriented fiat wood shavings arranged substantially parallel to the outer face of the finished board; and an adhesive substance connecting said fiat wood shavings directly to one another and to said core whereby said fiat wood shavings firmly adhere to one another and to said porous core so as to provide on at least one side of said core a firmly adhering surface layer being substantially impervious to water and having a high tensile strength;

22. A composite wooden board comprising in combination a core layer of randomly arranged splinted-shaped wood particles providing air spaces between themselves, a binder substance firmly connecting said randomly arranged wood particles without filling said air spaces so that said randomly arranged wood particles firmly adhere to one another and provide a porous core havinggood heat insulating properties; an outer layer arranged on oneface of said heat insulating porous core and having a thickness which is small as compared to the thickness of said core, said outer layer comprising superposed unoriented fiat wood shavings arranged substantially parallel to the outer faces of the finished board; and an adhesive substance connecting said flat wood shavings to one another and to said porous core whereby said fiat wood shavings firmly adhere to one another and to said porous core so as to provide on one side of said porous core a firmly adhering surface layer being substantially im- FRED FAHRNI.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 291,164 Dickman et al. Jan. 1, 1884 1,063,941 Lewis June 3, 1913 2,066,734 Loetscher Jan. 5, 1937 2,067,012 Loetscher Jan. 5, 1937 2,120,137 Mason June 7, 1938 2,124,921 Lederer July 26, 1938 2,397,936 Glidden et a1. Apr. 9, 1946 2,446,304 Roman Aug. 3, 1948 

1. A COMPOSITE WOODEN BOARD COMPRISING IN COMPRISING IN COMBINATION A CORE LAYER OF RANDOMLY ARRANGED WOOD PARTICLES PROVIDING AIR SPACES BETWEEN THEMSELVES; A BINDER SUBSTANCE FIRMLY CONNECTING SAID RANDOMLY ARRANGED WOOD PARTICLES WITHOUT FILLING SAID AIR SPACES SO THAT SAID RANDOMLY ARRANGED WOOD PARTICLES FIRMLY ADHERE TO ONE ANOTHER AND PROVIDE A POROUS CORE HAVING GOOD HEAT INSULATING PROPERTIES; AN OUTER LAYER ARRANGED ON ONE FACE OF SAID POROUS CORE AND HAVING A THICKNESS WHICH IS SMALL AS COMPARED TO THE THICKNESS OF SAID CORE, SAID OUTER LAYER CONSISTING OF SUPERPOSED UNORIENTED FLAT WOOD SHAVINGS; AND AN ADHESIVE SUBSTANCE CONNECTING SAID FLAT WOOD SHAVINGS DIRECTLY TO ONE ANOTHER AND TO SAID POROUS CORE WHEREBY SAID FLAT WOOD SHAVINGS FIRMLY ADHERE TO ONE ANOTHER AND TO SAID POROUS CORE SO AS TO PROVIDE ON ONE SIDE OF SAID POROUS A FIRMLY ADHERING SURFACE LAYER BEING SUBSTANTIALLY IMPERVIOUS TO WATER AND HAVING A HIGH TENSILE STRENGTH. 